Out-of-band data communication between network transceivers

ABSTRACT

Out-of-band data communication of diagnostic or other data is performed using transceivers in a data or communication network. A light beam or other carrier is modulated with high-speed data and out-of-band data to create a double modulated data signal. A physical layer signal is created that includes modulations of the double modulated signal. The physical layer signal is transmitted onto a physical link. The diagnostic or other data can be transmitted in the out-of-band signal without substantially reducing or otherwise interfering with the transmission rate of the high-speed data.

BACKGROUND OF THE INVENTION

1. The Field of the Invention

The invention generally relates to the field of data transmission incommunication networks. More specifically, the invention relates tosimultaneous transmission of high-speed data and out-of-band data.

2. Description of the Related Art

Modem day communication is, in large part, accomplished by transmittingand receiving large amounts of digital data. Digital data signals can beused to transmit information such as database information, financialinformation, personal and business information, and the like. Inaddition, digital data signals can be used to transmit voice, video,images etc.

Commonly, digital communication is accomplished using a model known asthe Open Systems Interconnection (OSI) model. The OSI model defines aframework for accomplishing digital communications with seven layers onclients communicating in a network. These seven layers are understood bythose of skill in the art, and include from the highest level to thelowest level: the application layer, the presentation layer, the sessionlayer, the transport layer, the network layer, the data link layer, andthe physical layer. At the application layer, data is used in end userprocesses. Data is packaged by each of the other layers of the OSI modelprior to being sent using the physical layer. The physical layer defineshow the data is actually sent on the network, such as by electricalsignals, light carried on optical fibers, radio signals etc. Thus, atthe physical layer, actual voltages, light levels and radio amplitudesor frequencies are defined as having certain logical values.

At the physical layer, one method of communicating digital data involvesthe use of transceivers. A transceiver includes a signal power sourceincluding electronic hardware for transmitting data signals along aphysical link such as a copper wire link or fiber-optic link. The signalpower source may be a laser, electronic amplifier, radio transmitter andthe like. The transceiver may also include a physical layer signalreception element to receive physical layer signals. The physical layerreception element may be a photodiode, an electronic amplifier, a radioreceiver, or the like.

The transceiver may include electronic hardware for decoding signalsthat are sent between clients into data signals, such as binaryrepresentations, readable by digital devices or hosts to which thetransceiver is connected. The transceiver may also include electronichardware for encoding signals that are sent between clients from abinary representation to a physical layer level signal that can betransmitted across a physical link. Thus, in one example, a binaryrepresentation is converted to one of a modulated electronic signal, amodulated optical signal, a modulated radio signal or anotherappropriate signal.

Each transceiver is generally passive with respect to othertransceivers. This means that a transceiver simply sends and receivesdigital data that has been converted to a physical layer level signalwithout extracting or processing the information represented by thedigital data. In other words, transceivers do not generally communicatedata to one another for the benefit of the transceivers. Instead, thetransceivers communicate data to one another for the benefit of thehosts to which the transceivers are connected.

A transceiver may communicate data for the benefit of the transceiver tothe connected host device. For example, a transceiver may be configuredto generate digital diagnostic information by monitoring the health ofthe transceiver. The transceiver may then communicate information aboutthe health of the transceiver to its connected host. This communicationtypically takes place on an I²C or MDIO bus for communicating betweenintegrated circuits. As a transceiver deteriorates due to age, componentfailure or other reasons, the host may be aware of the deteriorationusing such communications received from the transceiver.

Digital diagnostics logic (also referred to herein as “digitaldiagnostics”) may be used to handle various tasks and to generatemonitoring and operating data. These task and data may include some ofthe following:

-   -   Setup functions. These generally relate to the required        adjustments made on a part-to-part basis in the factory to allow        for variations in component characteristics such as laser diode        threshold current.    -   Identification. This refers to general purpose memory, typically        EEPROM (electrically erasable and programmable read only memory)        or other nonvolatile memory. The memory may be accessible using        a serial communication standard, that is used to store various        information identifying the transceiver type, capability, serial        number, and compatibility with various standards. While not        standard, this memory may also store additional information,        such as sub-component revisions and factory test data.    -   Eye safety and general fault detection. These functions are used        to identify abnormal and potentially unsafe operating parameters        and to report these to the host and/or perform laser shutdown,        as appropriate.    -   Temperature compensation functions. For example, compensating        for known temperature variations in key laser characteristics        such as slope efficiency.    -   Monitoring functions. Monitoring various parameters related to        the transceiver operating characteristics and environment.        Examples of parameters that may be monitored include laser bias        current, laser output power, receiver power levels, supply        voltage and temperature. Ideally, these parameters are monitored        and reported to, or made available to, a host device and thus to        the user of the transceiver.    -   Power on time. The transceiver's control circuitry may keep        track of the total number of hours the transceiver has been in        the power on state, and report or make this time value available        to a host device.    -   Margining. “Margining” is a mechanism that allows the end user        to test the transceiver's performance at a known deviation from        ideal operating conditions, generally by scaling the control        signals used to drive the transceiver's active components.    -   Other digital signals. A host device may configure the        transceiver so as to make it compatible with various        requirements for the polarity and output types of digital inputs        and outputs. For instance, digital inputs are used for        transmitter disable and rate selection functions while outputs        are used to indicate transmitter fault and loss of signal        conditions. The configuration values determine the polarity of        one or more of the binary input and output signals. In some        transceivers, these configuration values can be used to specify        the scale of one or more of the digital input or output values,        for instance by specifying a scaling factor to be used in        conjunction with the digital input or output value.

The data generated by the digital diagnostics described above isgenerally only available to the host on which a transceiver isinstalled. Thus, when troubleshooting problems with individualtransceivers, a user must access the host on which the transceiver isinstalled to discover any digital diagnostic data about a transceiver.This may cause various difficulties when the host and transceiver arelocated in a remote location such as on the ocean floor or in remotedesert locations. Further, some applications make use of repeaters,which are transceiver pairs that simply receive an optical data stream,amplify the optical data stream, and retransmit the optical data stream.In repeater applications, the digital diagnostic data is stored on therepeater. Thus to troubleshoot the repeater, the repeater must bephysically retrieved and queried for any digital diagnostic data.

Some protocols exist where digital diagnostic data can be sent as partof the high-speed data sent on an optical link. However, this generallyinvolves sending the data in some specially defined packet or portion ofa packet. Thus to retrieve the digital diagnostic data, the high-speeddata must be disassembled such as by a framer, the digital diagnosticdata extracted, and the high-speed data reassembled. Additionally, ifdigital diagnostic data is to be added by a transceiver in a chain oftransceivers, the high-speed data must be disassembled and the digitaldiagnostic data added in the appropriate portion of the high-speed data,and the high-speed data, including the digital diagnostic data,reassembled. To disassemble and reassemble a high-speed data signalrepresents a significant and unwanted cost in terms of data processing.Additionally, there are time delays as the data is disassembled andreassembled prior to retransmission of the data from link to link.

In other presently existing systems, the digital diagnostic data may besent in a high-speed data signal that includes multiple channels whereone of the channels is reserved for high-speed data. This implementationcannot be used in single channel systems. Further, the use of a channelfor diagnostic data reduces the amount of other high-speed data that canbe transmitted. Also, the cost of disassembling and reassembling thehigh-speed data signal remains as the channel with the digitaldiagnostic data must be extracted from the high-speed data signal toobtain the digital diagnostic data and re-added to the high-speed datasignal when the high-speed data signal is passed to other links in anetwork.

Another challenge that arises with transceivers presently in the artrelates to negotiating data rates along a channel. Communication at thephysical layer includes protocols that specify, among other things, thedata rate at which communication may be accomplished. Some protocolshave variable communication data rates. This may be useful as thequality of the links between hosts vary. A lower quality link oftenrequires lower data rates to avoid errors. Additionally, data rates maybe faster on later produced devices as technology advances. A protocolthat allows for different data rates is the fiber channel protocol thatsupports data rates of 1, 2 and 4 Gigabits/second. Typically, a linkbetween two devices requires that the device communicate at the samedata rate. Where devices are capable of communicating at different datarates, the devices, such as host devices, negotiate the data rate atwhich communications will occur. Presently existing negotiationprotocols are complex and may require inordinate amounts of network andcomputing resources to properly negotiate a data rate.

BRIEF SUMMARY OF THE INVENTION

Embodiments of the present invention relate to transceivers having asignal power source, such as a laser driver and laser, which isconfigured to produce a physical link signal, such as an optical signal,for transmission across a physical link, such as a fiber optic cable.These transceivers also include a high-speed data modulator connected tothe signal power source. An out-of-band data modulator is also connectedto the signal power source. The signal power source creates an outgoingdouble modulated signal in response to the high-speed data modulationand out-of-band data modulation. The outgoing double modulated signalincludes high-speed data and out-of-band data.

Other embodiments of the invention relate to methods of transmittingdata on a physical link. Such methods include modulating a signal withhigh-speed data and out-of-band data to create a double modulated datasignal. The double modulated signal is a physical layer signal fortransmission on a physical link. The physical layer signal, whichincludes modulations of the outgoing double modulated signal, istransmitted onto the physical link.

In this manner, embodiments of the invention enable out-of-band data tobe transmitted simultaneously with high-speed data on the high-speeddata physical link. This may allow for monitoring transceiver health,remotely configuring transceivers, authenticating transceivers etc.

These and other advantages and features of the present invention willbecome more fully apparent from the following description and appendedclaims, or may be learned by the practice of the invention as set forthhereinafter.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

In order that the manner in which the above-recited and other advantagesand features of the invention are obtained, a more particulardescription of the invention briefly described above will be rendered byreference to specific embodiments thereof which are illustrated in theappended drawings. Understanding that these drawings depict only typicalembodiments of the invention and are not therefore to be consideredlimiting of its scope, the invention will be described and explainedwith additional specificity and detail through the use of theaccompanying drawings in which:

FIG. 1 illustrates a connection between two host devices forcommunicating high-speed and out-of-band data;

FIG. 2A illustrates an eye diagram showing channel margins that may beused to modulate out-of-band data onto a high-speed data signal whilestill maintaining an appropriate extinction ratio;

FIG. 2B illustrates an eye diagram showing out-of-band data modulatedusing an average power setting of a transmitter;

FIG. 2C illustrates a high-speed data signal modulated with out-of-banddata where the out-of-band data is modulated on the average power of thehigh-speed data signal;

FIG. 2D illustrates an eye diagram showing out-of-band data modulatedusing an extinction ratio;

FIG. 2E illustrates a high-speed data signal modulated with out-of-banddata where the out-of-band data is modulated on the extinction ration ofthe high-speed data signal;

FIG. 2F illustrates an eye diagram showing out-of-band data modulatedusing peak power;

FIG. 2G illustrates a high-speed data signal modulated with out-of-banddata where the out-of-band data is modulated on the peak power of thehigh-speed data signal;

FIG. 3A illustrates an apparatus for modulating out-of-band data ontothe average power of a high-speed data signal, where the apparatusincludes feedback from a monitor photodiode;

FIG. 3B illustrates an apparatus for modulating out-of-band data ontothe average power of a high-speed data signal;

FIG. 3C illustrates an apparatus for modulating out-of-band data ontothe extinction ratio of a high-speed data signal;

FIG. 3D illustrates an apparatus for modulating out-of-band data ontothe peak power of a high-speed data signal;

FIG. 3E illustrates an apparatus for modulating out-of-band data ontothe peak power of a high-speed data signal;

FIG. 4 illustrates an apparatus for receiving a double modulated signaland for extracting high-speed data and out-of-band data from the doublemodulated signal;

FIG. 5 illustrates a transceiver including hardware for sending andreceiving high-speed data and out-of-band data;

FIG. 6 illustrates an alternate embodiment of a transceiver including anintegrated circuit chip that includes various components for sending andreceiving high-speed and out-of-band data;

FIG. 7 is a diagram illustrating frequency bandwidths includingfrequencies at which signals are filtered out of a data link,frequencies at which high-speed data is typically transmitted, andfrequencies available for out-of-band data communications; and

FIG. 8 illustrates a network of repeaters configured to communicatehigh-speed and out-of-band data.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention include systems and methods formodulating high-speed data and out-of-band data as a double modulatedsignal. The double modulated signal is transmitted on a physical linkbetween components in a network of connected hosts. Thus, high-speeddata that is ordinarily transmitted on a physical link can betransmitted with out-of-band data on the same physical link. This allowsfor the transmission of information such as diagnostic information,authentication information, rate negotiation information, configurationinformation etc.

The term “high-speed data,” as used herein, does not refer to anyparticular defined bandwidth or frequency of data. Rather, high-speeddata refers to data typically transmitted on a network such as the datatypically transmitted for the benefit of the various hosts on a network.High-speed data may also be referred herein as in-band data which is areference to the communication band typically used by host systems tocommunicate data. High-speed and in-band data are distinguished fromout-of-band data which is typically used to transmit data fromtransceiver to transceiver for the use of the transceivers. While a hostmay subsequently receive the out-of-band data, the host usually receivesthe out-of-band data from a transceiver through a low speed bus such asan I²C or MDIO bus. This is contrasted to high-speed data which istypically received by a host from a transceiver through some type ofhigh-speed data interface. Notably, a host may also produce theout-of-band data and transmit the out-of-band data to a transceiver on alow speed bus.

Referring now to FIG. 1, an embodiment of the invention that encodesout-of-band data by modulating a high-speed data signal is shown. FIG. 1shows a host device 102 for use in fiber optic communications. The hostdevice includes a transmitter optical subassembly (TOSA) 104 fortransmitting signals across a physical link 106. The host device 102also includes a receiver optical subassembly (ROSA) 108 for receivingoptical signals across a physical link 110. The TOSA 104 is connected toa high-speed data control 112, which may include a high-speed modulatorthat modulates the power output of a signal power source such as a laserin the TOSA 104 such that the high-speed data is converted to a formthat can be transmitted across the physical link 106. As shown in FIG.1, the high-speed data control 112 modulates the TOSA 104 to produce ahigh-speed physical layer data signal 116. Also connected to the TOSA104 is an out-of-band data control 114. The out-of-band data control 114further modulates the laser in the TOSA 104 using an out-of-band datamodulator such that an out-of-band data stream 118 is modulated onto thehigh-speed data signal 116 to produce an outgoing double modulatedsignal 122 that includes high-speed and out-of-band data.

In the example shown, the modulations of the out-of-band data appear asa change in peak power 120 of the outgoing double modulated signal 122.Thus the outgoing double modulated signal 122 includes both high-speeddata and out-of-band data. The out-of-band data may be modulated using anumber of different modulation techniques including but not limited tophase shift keying, binary phase shift keying, quadrature phase shiftkeying, and Manchester encoding. The out-of-band data may actually havea frequency range that is orders of magnitude less than the in-banddata. However, to illustrate the principle of double modulation in asimple graphical form, the frequency of the out-of-band data stream 118is illustrated in FIG. 1 as having only a slightly lower frequency thanthe high-speed data signal 116. Regardless, the principles of thepresent invention are not limited to the relative frequency between theout-of-band data stream 118 and the high-speed data signal 116.

To perform receiving functions, the ROSA 108 includes a signal receptionelement such as a photodiode that receives an incoming double modulatedsignal. The ROSA 108 sends all or portions of the incoming doublemodulated signal to the out-of-band data control 114 and the high-speeddata control 112. The out-of-band data control 114 may include anout-of-band detector that extracts the out-of-band data from theincoming double modulated signal. The high-speed data control 112 mayinclude a high-speed data amplifier that extracts high-speed data fromthe incoming double modulated signal.

Referring now to FIG. 2A principles of embodiments of the presentinvention may be understood in reference to an eye diagram 200. The eyediagram 200 is a graphical representation of signal quality formed bythe superposition of multiple bits of data. The eye diagram 200 includesshaded regions which are forbidden zones 202. If the boundary of a bitfalls within the forbidden zones 202, that bit will be interpreted as anerror. Thus data transmitted across a physical link must be transmittedso that the data does not fall within the forbidden zones 202. Certainspecifications require that only a limited number of bits be interpretedas errors. This is usually expressed as a required bit error rate (BER).The BER can be described or quantified based on the eye diagram. Theappropriate BERs may be expressed in a communications standard, such asthe 10Gigabit Ethernet standard, which specifies BERs no greater that10⁻¹².

Bit error rates may also be specified by customer expectations orrequirements. Often the BER required by customers purchasingcommunication equipment exceeds the BER specified by a particularcommunication standard. The BER is a function of the extinction ratioand the average power (Pave in FIG. 2A) received by a transceiver.Physical layer specifications often specify BER as a minimum and maximumextinction ration. The extinction ratio is the ratio of the power levelreceived by a transceiver when a “1” high-speed bit is transmitted (P₁in FIG. 2A) to the power level received by a transceiver when a “0”high-speed bit is transmitted (P₀ in FIG. 2A). Thus, the extinctionratio is expressed as P₁/P₀. A particular extinction ratio will cause asufficient number of high-speed bits to fall within a bit margin 204that is outside of the forbidden zone 202 to achieve a required BER.

Also shown in FIG. 2A, is a channel margin 206 that defines power levelswhere high-speed data bits can still exist and not be interpreted aserrors. The channel margin 206 may facilitate embedding out-of-band dataonto a high-speed data signal.

In one embodiment of the invention, the out-of-band data may be embeddedonto the high-speed data by modulating the average power of thehigh-speed bits transmitted. This example is illustrated by the eyediagram in FIG. 2B. The eye diagram is modulated within the channelmargins 206. In FIG. 2B, the eye diagram has the same extinction ratiowhether a “0” out-of-band data bit or a “1” out-of-band data bit isbeing transmitted. In other words,P_(1-OOB0)/P_(0-OOB0)=P_(1-OOB1)/P_(0-OOB1) where P_(1-OOB0) is thepower transmitted with a “1” high-speed bit and a “0” out-of-band bit,P_(0-OOB0) is the power transmitted with a “0” high-speed bit and a “0”out-of-band bit, P_(1-OOB1) is the power transmitted with a “1”high-speed bit and a “1” out-of-band bit and P_(0-OOB1) is the powertransmitted with a “0” high-speed bit and a “1” out-of-band bit. Thus,an appropriate BER can be maintained while modulating the out-of-banddata onto the high-speed data.

Illustratively, FIG. 2C shows an out-of-band bit stream modulated onto.a high-speed bit stream. Notably, the bit streams in FIG. 2C are notdrawn to scale. Typically, an out-of-band bit stream, in the embodimentshown, may be NRZ modulation at 19200 baud, whereas the high-speed datais at 2.5 Gbits/s. In this example, this results in about 130,000high-speed bits per out-of-band bit. Thus, for clarity, FIG. 2C is notdrawn to scale. FIG. 2C shows the average power of an optical signalmodulated according to an out-of-band bit stream.

In an alternate embodiment of the invention shown in FIGS. 2D and 2E,the out-of-band data is modulated onto the extinction ratio. In thisexample, the average power remains constant, while the peak power, atboth the highest and lowest power outputs, is modulated according to anout-of-band bit stream. FIG. 2D shows that the extinction ratio when a“1” out-of-band bit is being transmitted is greater than when a “0”out-of-band bit is being transmitted. Viewed alternatively as shown inFIG. 2E, when a “1” out-of-band bit is transmitted, the high-speed “1”bits are transmitted with a higher power than when a “0” out-of-banddata bit is transmitted. Additionally, when a “1” out-of-band bit isbeing transmitted, a “0” high-speed bit is transmitted with less powerthan when a “0” out-of-band bit is being transmitted. Thus theout-of-band data behaves similar to an amplitude modulation of thehigh-speed data.

Another embodiment of the invention, as shown in FIGS. 2F and 2G,modulates a combination of the peak power of the high-speed data and theaverage power of the high-speed data with out-of-band data. In theexample shown, the out-of-band bit stream is modulated onto thehigh-speed “1” bits. Thus in this case, the extinction ratio of thetransmitted optical signal is higher when a “1” out-of-band bit is sentthan when a “0” out-of-band bit is sent. Viewed differently, the “1”high-speed bits are transmitted with more power when an out-of-band “1”bit is transmitted than when an out-of-band “0” bit is transmitted. Thisembodiment may help to simplify high-speed data receiver designs.

Referring now to FIGS. 3A and 3B, transmitter designs are illustratedthat can be used to modulate the average power of a high-speed datasignal with out-of-band data. A transmitter 300 includes a laser driver302 connected to a laser 304. The laser driver 302 accepts as one input,an extinction ratio command 306. The extinction ratio command 306controls the extinction ratio of signals transmitted by the transmitter300. The laser driver 302 further includes a high-speed data input 308,which is a differential input accepting high-speed electrical signals.Using the high-speed data input 308, the laser driver modulates thelaser 304 output power.

The transmitter 300 includes various components in a bias circuit forcontrolling the average power output of the laser 304. The bias circuitincludes a transistor 310 that controls a bias current through the laser304. The transistor 310 is controlled by an amplifier 312. The amplifier312 has, as one input, the sum of an average power command 314 and anout-of-band data signal 316. The out-of-band data signal 316 causes theaverage power output of the laser 304 to be modulated according to theout-of-band data signal 316. Modulating using the laser driver 302 andthe bias circuit creates a double modulated signal including bothhigh-speed and out-of-band data. In the example shown, the average powercommand 314 represents 97% of the amplifier 312 input whereas theout-of-band data signal 316 represents 3% of the amplifier 312 input.These are only exemplary numbers and other ratios may be used. Theamplifier 312 has as feedback, a signal from a monitor photodiode 318.The monitor photodiode 318 monitors the output power of the laser diode304 and allows a current to flow through the monitor photodiode 318 thatis proportional to laser output power. This current is used to generatea signal that is fed into the amplifier 312 as a feedback signal. Inthis way, the average power output of the laser 304 can be maintained ata constant level dictated by the combination of the average powercommand signal 314 and the out-of-band data signal 316.

FIG. 3B illustrates another transmitter that may be used to modulate theaverage power output of the laser 304 with out-of-band data. Thetransmitter 320 of FIG. 3B is similar to the transmitter 300 of 3A.However, the transmitter of 3B excludes the monitor photodiode 318 ofFIG. 3B. Instead, amplifier 312 receives a feedback signal that isessentially proportional to the current through the laser 304.

FIG. 3C illustrates a transmitter 322 that may be used to modulateout-of-band data as a modulation of the extinction ratio such as themodulation shown in FIGS. 2D and 2E. The transmitter 322 includes alaser driver 302 which has as one input the high-speed data signal 308to modulate the laser 304. Another input into the laser driver is thecombination of an extinction ratio command signal 306 and theout-of-band data signal 316. This causes the laser 304 to produce adouble modulated optical signal including both the high-speed data andthe out-of-band data. The transmitter 322 also includes circuitry tocontrol the average power output of the laser 304 such as the transistor310, the amplifier 312 and the monitor photodiode 318. As with theembodiment shown in FIG. 3B, the monitor photodiode 318 may beeliminated in favor of other types of average power feedback.

FIGS. 3D and 3E illustrate transmitter circuits for modulating acombination of the peak power of the high-speed data and the averagepower of the high-speed data with out-of-band data such as isillustrated by the modulation shown in FIGS. 2F and 2G. The transmitter324 shown in FIG. 3D includes a laser driver 302 that has a differentialhigh-speed data input 308 for modulating the laser 304 with high-speeddata. The laser driver also has an input that is the combination of anextinction ratio command 306 and an out-of-band data signal 316. Theoutput power of the laser 304 is further modulated by the bias circuitryincluding the amplifier 312 and transistor 310. The amplifier 312 has asone input a combination of an average power command 314 and theout-of-band data signal 316. The modulation of the out-of-band datasignal causes the amplifier 312 and transistor 310 to modulate theaverage power of the laser 304. Notably, to obtain the modulation shownin FIGS. 2F and 2G, when the modulation at the laser driver has a ratioof 97% extinction ratio command to 3% out-of-band data, the ratio ofaverage power command is 98.5% to 1.5% out-of-band data. As mentionedabove, those of skill in the art will recognize that other ratios may beused such as 95% extinction ratio command to 5% out-of-band data whenthe average power command is 97.5% to 2.5% out-of-band data. Notably,only two examples of ratios have been demonstrated here when in factmultiple other examples are contemplated by embodiments of theinvention. The channel margin 206 allows for, in theory, an unlimitednumber of ratios for each of the embodiments set forth above. Inpractice, the ratios are limited by the sensitivity of variouscomponents within a system.

FIG. 3E illustrates yet another embodiment of a transmitter thatmodulates a combination of the peak power of the high-speed data and theaverage power of the high-speed data with out-of-band data such as isillustrated by the modulation shown in FIGS. 2F and 2G. FIG. 3E shows atransmitter 326. The transmitter 326 includes a current source 328 forbiasing the laser 304. The current source 328 has as an input ahigh-speed data “0” level command 330 that defines the amount of currentsupplied to the laser 304 when a high-speed data “0” bit is to betransmitted. A laser driver 302 is connected to the laser 304. The laserdriver receives as one input a high-speed data signal 308 that modulatesthe laser power according to the high-speed data signal 308. Notably,the laser driver 302 is shown modulating using only a single drivesignal. The laser driver 302 will nonetheless receive a differentialsignal which will be converted by the laser driver 302 to a single drivesignal for modulating the laser 304. The laser driver 302 also includesan input that is the combination of a high-speed data “1” level command332 and the out-of-band data signal 316. The high-speed data “1” levelcommand 332 defines the additional power that is output by the laser 304when a high-speed data “1” bit is to be transmitted. By combining thehigh-speed data “1” level command 332 with the out-of-band data signal316, the out-of-band data is modulated onto the “1” bits of thehigh-speed data as is shown in FIGS. 2F and 2G.

Some embodiments of the invention further include an encoder forencoding the out-of-band data prior to using the out-of-band data formodulating the laser 304. The encoder may be used to encode theout-of-band data using encoding techniques such as Manchester encoding,phase shift keying and the like.

Referring now to FIG. 4, an exemplary receiver for receiving an incomingdouble modulated signal is shown. Receiver 400, in this example includesa signal reception element that, in this case, is a photodiode 402 forreceiving a physical layer signal that is an optical signal, from aphysical link. The photodiode 402 converts the physical layer signalinto an incoming double modulated electronic signal that in this exampleis a current through the photodiode 402. The photodiode 402 is connectedto a photodiode current monitor 404 that monitors the current throughthe photodiode 402. The current monitor 404 is connected, in the exampleshown, to a peak detector 408 that can be used to create a signal thatcan be fed into digital diagnostics 414 and an out-of-band detector 416.The digital diagnostics 414 monitors at least one of the average power,peak power, extinction ratio of a signal, etc received by the photodiode402. This information can be used to, among other things, monitor anddetermine the health of transceivers in a network.

The out-of-band data detector 416 converts the average power, peak poweror extinction ratio of the optical signal received at the photodiode 402into an out-of-band data stream. This out-of-band data stream is fedinto a UART 418 and further into a microprocessor 420 for any suitableuse of the out-of-band data stream. In embodiments where the out-of-banddata has been modulated using modulation techniques such as Manchesterencoding, phase shift keying and the like, the out-of-band data detector416 includes a demodulator to demodulate the out-of-band data.

In one embodiment of the invention, the out-of-band data detector may bea commercial infrared (IR) remote control decoder, such as thosetypically used in television remote controls or other such equipment.Suitable decoders include receivers such as T2525, T2527 and U2538B,available from Amtel Corporation in San Jose, Calif. IR remote controldecoders are especially well adapted to receiving out-of-band datasignals. IR remote control decoders are designed to decode signalsderived from ambient lighting, such as incandescent and other lights,and modulated IR light signals from a control transmitter, and toextract the modulated control signals from the background noise of theambient light. This situation is somewhat analogous to embedding arelatively small out-of-band data signal on a much larger high-speeddata signal. Thus, the IR remote control decoders may provide a way toimplement embodiments of the present invention.

Small currents are caused in the photodiode 402 when optical signalscontact the photodiode. These small currents pass through a high-speeddata input 406 and are fed into a high-speed data amplifier, which, inthis example, is a transconductance amplifier 422. The transconductanceamplifier 422 converts the current from the high-speed data input 406into a differential high-speed data voltage signal. The differentialhigh-speed data voltage signal passes through filtering capacitors 424to a post amplifier 426. The filtering capacitors 424 remove frequenciesbelow a given threshold such that only high-speed data is transmitted tothe post amplifier 426. The post amplifier 426 performs appropriatesignal processing of the high-speed data signal. This processedhigh-speed data signal is then sent through additional filteringcapacitors 428 and finally to output terminals 430, where it isavailable to a device having need of the high-speed data signal, such asa host device.

Referring now FIG. 5, an embodiment of the invention that includes atransceiver for receiving and transmitting high-speed data andout-of-band data is shown. The transceiver 500 includes a high-speedtransmit port 502 for receiving high-speed electronic data. Thehigh-speed electronic data may be received from a host device in whichthe transceiver 500 is installed. The high-speed electronic data istransmitted through filtering capacitors 504 to a laser driver 506. Thelaser driver amplifies the high-speed electronic data to produce adriving signal which is then passed to a TOSA 510 that converts thedriving signal into optical data. The laser driver 506 is furtherconnected to a controller 512. The controller receives I²C data at anI²C port 514. The controller delivers the data received from the I² Cport 514 through an out-of-band transmission UART 516 to the laserdriver 506.

Embodiments of the invention also contemplate out-of-band data beingproduced within the transceiver 500 by the controller chip 512 or othercircuitry in the transceiver. For example, the out-of-band data may bedigital diagnostic data such as, but not limited to, setup functions,identification information, eye safety and general fault detection,temperature compensation functions, monitoring functions, power on time,margining, and the like. The digital diagnostic data produced by thecontroller chip may be sent as out-of-band data. Notably, the digitaldiagnostic data may also be produced, in whole or in part, by the hostdevice and transmitted to the transceiver across the I²C bus. Thus,out-of-band data may derive from multiple sources including a hostdevice, or directly from functions performed within a transceiver.

The laser driver 506 encodes the out-of-band data received from the I²Cport 514 onto the driving signal for driving the TOSA 510 and ultimatelya laser 528 such that out-of-band data is modulated together with ahigh-speed data signal which is then output as an outgoing doublemodulated optical signal from the TOSA 510. Optical data is received bythe transceiver 500 at the ROSA 518. The optical data may be an incomingdouble modulated optical signal that includes both high-speed data andout-of-band data. The optical signal is converted to an electronicsignal by the ROSA 518. The post amplifier 520 extracts high-speedelectronic data which is then fed to a high-speed output port 522 wherethe high-speed data is made available to a host device in which thetransceiver 500 is installed. A decoder 526 extracts out-of-band datafrom an electronic signal generated by a photodiode current monitor 530in the ROSA 518 which is then fed into an out-of-band reception UART 524in the controller 512. The decoder 526 may also include demodulationfunctionality when the as-out-of-band data has been modulated using somemodulation technique. The out-of-band data, in this example, ismodulated at some low frequency. Low frequency as used in this contextdoes not specify any defined bandwidth other than a bandwidth lower thanthe high-speed data. Bandwidths for the out-of-band data are discussedin more detail below in conjunction with the description of FIG. 7.

Referring now FIG. 6 an alternate embodiment of a transceiver is shown.The transceiver 600 in FIG. 6 may be, for example, an XFP transceiver.The transceiver 600 is similar to the transceiver 500 shown in FIG. 5and data communications follow a similar path. The transceiver 600includes a single chip 602 that includes a clock and data recoverycircuit 604. The clock and data recovery circuit 604 also includes apost amplifier 606 for performing digital signal processing on thesignals received from the ROSA 618. The clock and data recovery circuit604 is connected to a microprocessor 608 that receives out-of-band dataextracted by the clock and data recovery circuit 604, which alsoincludes circuitry to perform out-of-band data detector functions. Onthe transmit side of the transceiver 600, the microprocessor 608 isconnected to a clock and data recovery circuit for sending out-of-banddata.

The clock and data recovery circuit 610 is included in the chip 602. Theclock and data recovery circuit 610 is connected to a laser driver 612.In one embodiment of the invention, such as the example shown in FIG. 6,the laser driver 612 is also included on the chip 602. The laser driver612 is connected to a TOSA 614. The clock and data recovery circuit mayinclude portions of a high-speed data modulator and out-of-band datamodulator for driving the laser driver 612. The example shown in FIG. 6illustrates how various embodiments of the invention may incorporateelements for accomplishing the sending and receiving of the out-of-banddata in an integrated single chip. Those skilled in the art appreciatethat various combinations of components used for transmitting andreceiving out-of-band data may be incorporated on a single chip withinthe scope of embodiments of the present invention.

Referring now to FIG. 7, a graph illustrating how out-of-band digitaldata may be transmitted across a physical link is shown. The out-of-banddata is considered in the context of the frequency response of data oncomponents associated with the transmission of data on the physicallink. Ordinarily, high-speed digital data is transmitted within certainfrequency parameters or within a certain data frequency bandwidth 702.This is often a function of the frequency, i.e. 1 gigabit, 2 gigabit, 4gigabit etc, that is specified for a given communications protocol. Thismay also be a function of filters. As shown in FIGS. 4 and 5, filteringcapacitors such as filtering capacitors 424, 428, 504 and 508 are usedto filter out low frequency signals. These filtering capacitors, in oneembodiment of the invention are designed to filter out frequencies below30 kHz. High-speed digital data is usually transmitted such that thesignal is DC balanced. This is done by transmitting, on the average, anequal number of 1s and 0s. A signal that is DC balanced, in thiscontext, does not have a DC value. This allows the entire signal to passthrough filtering capacitors, such as filtering capacitors 504 and 508shown in FIG. 5. The filtering capacitors block all DC portions of asignal as well as other low frequency signals. Several techniques may beused to DC balance a signal. For example, 8 bits of binary data may betransmitted using a 10 bit word. The extra bits are used to balance thenumber of 1s and 0s. This type of coding may be used, for example, with1 to 4 gigabits/second Ethernet and Fiber Channel links. This type ofcoding usually results in the signal being transmitted at frequenciesabove 100 Khz. For telecom systems such as SONET or SDH, and 10G Datacomlinks, scrambling techniques can be used to randomize the bit-stream andthus balance the 1s and 0s. As mentioned above, each of these DCbalancing techniques, alone or in combination with filtering, results inthe high-speed data being within a high-speed data bandwidth 702.

Out-of-band data can thus be transmitted at frequencies below, or insome embodiments above, the high-speed data bandwidth 702. The databandwidth for modulating out-of-band data is shown in FIG. 7 as theout-of-band data bandwidth 704. Thus, the out-of-band data resides inthe out-of-band data bandwidth 704. To accomplish out-of-bandmodulation, in one embodiment of the invention, a modulated data signalthat has been modulated with high frequency data is further modulatedwith a data stream of out-of-band data within frequencies within theout-of-band data bandwidth 704.

Referring now to FIG. 8, an embodiment of the invention that allows fortransmission of out-of-band data between repeaters in a datatransmission range extension embodiment is shown. Some long-haul datatransmission applications require that intermediary repeaters be used toensure that data of suitable quality can be transmitted across the longhaul data link. For example, transmission along a fiber-optic cable fromone end of the United States to the other end of the United States mayrequire intermediary repeaters to accomplish the transmission withsuitable signal quality. FIG. 8 shows a first repeater 802 that includesa TOSA 804 and a ROSA 806. The repeater 802 receives a signal at theROSA 806. The signal is passed to a signal processor 808 that mayperform various digital signal processing tasks, such as removing noise,boosting signal power or other tasks to improve the quality of thesignal. The processed signal is then passed to the TOSA 804, where itmay be further retransmitted by repeaters 810 and 812. Repeater 802 alsoincludes out-of-band logic such a microprocessor 814 that, among otherthings, may be used to extract and insert out-of-band data onto thesignal sent and received by the repeater 802.

In one exemplary use of the repeater 802, digital diagnostic informationfor the repeater 802 is sent as out-of-band data through a network ofrepeaters, such as a network that includes repeaters 802, 810 and 812.The out-of-band data may be concatenated by each of the repeaters in thechain to include digital diagnostic information for each of therepeaters. Thus, the health of repeaters in the communication networkcan be monitored by a device remote from the repeaters. One example ofwhere this is useful is a network in which a repeater is located in aremote location, such as a rural area, an uninhabited region, or on theocean floor. When troubleshooting network problems, it may beprohibitively expensive to physically retrieve and test repeaters.However, where diagnostic information for each of the repeaters isincluded in out-of-band communications, the health and status of therepeater may be monitored remotely such that it is unnecessary tophysically retrieve and test the repeater.

In one embodiment of the invention, the out-of-band data that includesdigital diagnostic information from each of the repeaters may also beused to monitor the health of fiber optic links between the repeaters.For example, when the digital diagnostic information includes the powerof a transmitted signal and the power of a received signal, calculationscan be done by subtracting the power received by a receiving repeaterfrom the power sent by a sending repeater to the receiving repeater.Significant power loss may indicate the need to repair or replace a linkbetween repeaters.

In another embodiment of the invention, configuration information may besent to a remote host, repeater or other device. This helps to avoid theexpensive prospect of physically retrieving or being physically in thepresence of the device to configure the device. Configurationinformation may include, for example, instructions for the device toshut off, information designating a communication rate, informationindicating that laser power should be reduced or suspended etc.

In other embodiments of the invention, diagnostic information may berequested or automatically sent by a device. In one embodiment, a devicecan check to insure compatibility with other devices on a network byrequesting information such as identification information. In oneembodiment the identification information includes information about themanufacturer of a particular device such that a device requestingdiagnostic information may be able to determine that the particulardevice has been qualified for use with the device requesting diagnosticinformation.

In another embodiment of the invention, diagnostic information such assignal loss across a physical link, can be determined. For example, adevice may indicate the power at which a signal is transmitted. A devicethat receives a signal may indicate in out-of-band data the amount ofpower received. Thus by comparing the power of the signal sent with thepower of the signal received, the loss caused by the physical linkbetween the two devices can be determined.

In yet another embodiment of the invention, security can be maintainedbetween devices in a network by sending identification andauthentication information using the out-of-band data. Hardware orsoftware encoded encryption keys exist on devices within the networkwhich can be used to generate identification information or encryptedtokens for presenting to other devices in a network. Thus a secureconnection can be implemented between devices were those devices areappropriately matched to one another using hardware embedded encryptionkeys and the out-of-band data to communicate authentication andidentification information.

The present invention may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. The describedembodiments are to be considered in all respects only as illustrativeand not restrictive. The scope of the invention is, therefore, indicatedby the appended claims rather than by the foregoing description. Allchanges that come within the meaning and range of equivalency of theclaims are to be embraced within their scope.

1. A transceiver comprising: a signal power source adapted to produce aphysical layer signal for transmission across a physical link ahigh-speed data modulator that is coupled to the signal power sourcewherein the signal power source is configured to modulate a physicallayer signal with a high-speed data signal received from the high-speeddata modulator; and an out-of-band data modulator that is coupled to thesignal power source wherein the signal power source is configured tomodulate the physical layer signal in response to out-of-band datareceived from the out-of-band data modulator wherein modulation by thehigh-speed data modulator and out-of-band data modulator produces anoutgoing double modulated signal including high-speed data andout-of-band data.
 2. The transceiver of claim 1, wherein: thetransceiver is an optical transceiver; the signal power source comprisesa laser driver and laser; and the transceiver further comprises anaverage power bias circuit configured to control the average poweroutput by the laser, wherein the out-of-band data modulator is coupledto the average power bias circuit.
 3. The transceiver of claim 1,wherein: the transceiver is an optical transceiver; the signal powersource comprises a laser driver and laser; and the laser driver furthercomprises an extinction ratio command input configured to control theextinction ratio of a signal output by the laser, wherein theout-of-band data modulator is coupled to the extinction ratio commandinput.
 4. The transceiver of claim 1, wherein: the transceiver is anoptical transceiver; the signal power source comprises a laser driverand laser; the transceiver further comprises an average power biascircuit configured to control the average power output by the laser,wherein the out-of-band data modulator is coupled to the average powerbias circuit; and the laser driver further comprises an extinction ratiocommand input configured to control the extinction ratio of a signaloutput by the laser, wherein the out-of-band data modulator is coupledto the extinction ratio command input.
 5. The transceiver of claim 1,wherein: the transceiver is an optical transceiver; the signal powersource comprises a laser driver and laser; and the laser driver furthercomprises high-speed data 1 level command that defines the power outputby the laser when a high-speed data 1 is output, wherein the out-of-banddata modulator is coupled to the high-speed data 1 level command.
 6. Thetransceiver of claim 1, wherein the out-of-band modulator is configuredto modulate using at least one of phase shift keying, binary phase shiftkeying, quadrature phase shift keying, and Manchester encoding.
 7. Thetransceiver of claim 1, wherein the out-of-band data modulator isconfigured to modulate identification and authentication information. 8.The transceiver of claim 1, wherein the out-of-band data modulator isconfigured to modulate diagnostic information including the health ofthe transceiver.
 9. The transceiver of claim 1, wherein the out-of-banddata modulator is configured to modulate configuration data.
 10. Thetransceiver of claim 1 further comprising: a signal reception elementconfigured to receive physical layer signals from a physical link and toproduce an incoming double modulated signal from the physical layersignal; an out-of-band detector that is coupled to the signal receptionelement and is configured to extract out-of-band data from the incomingdouble modulated signal; a high-speed data amplifier that is coupled tothe signal reception element and is configured to extract high-speeddata from the incoming double modulated signal.
 11. The transceiver ofclaim 10, wherein the out-of-band detector comprises an IR receiver. 12.A method of transmitting data on a physical link comprising: modulatinga data signal with high-speed data; modulating the data signal without-of-band data wherein modulating the data signal with high-speed dataand out-of-band data creates an outgoing double modulated signal that isa physical layer signal for transmission on a physical link;transmitting the double modulated signal onto the physical link.
 13. Themethod of claim 12, wherein modulating the modulated data signalcomprises varying the average power the physical layer signal.
 14. Themethod of claim 12, wherein modulating the modulated data signalcomprises varying the peak power of the physical layer signal.
 15. Themethod of claim 12, wherein modulating the modulated data signalcomprises varying the extinction ratio of the physical layer signal. 16.The method of claim 12, further comprising: receiving an incoming doublemodulated signal that includes high-speed and out-of-band data;extracting high-speed data from the incoming double modulated signal;and extracting out-of-band data from the incoming double modulatedsignal.
 17. The method of claim 16, wherein extracting out-of-band datafrom the incoming double modulated signal comprises measuring averagepower of the incoming double modulated signal.
 18. The method of claim16, wherein extracting out-of-band data from the incoming doublemodulated signal comprises measuring peak power of the incoming doublemodulated signal.
 19. The method of claim 16, wherein extractingout-of-band data from the incoming double modulated signal comprisesmeasuring the extinction ratio of the incoming double modulated signal.20. The method of claim 12, wherein modulating the modulated data signalcomprises modulating the modulated data signal according to at least oneof phase shift keying, binary phase shift keying, quadrature phase shiftkeying, and Manchester encoding.
 21. A repeater for receiving andretransmitting digital data, the repeater comprising: a receiver adaptedto receive a data signal; a signal processor coupled to the receiver,the signal processor being adapted to perform processing tasks on thedata signal; a transmitter coupled to the signal processor, thetransmitter adapted to receive the data signal from the processor and totransmit the data signal; and out-of-band logic coupled to the signalprocessor, the out-of-band logic configured to extract and insertout-of-band data onto the data signal.
 22. The repeater of claim 21,wherein the out-of-band logic is configured to: extract out-of-band datafrom the data signal; concatenate data corresponding to digitaldiagnostic data for the repeater to the out-of-band data; and insert theout-of-band data including the data corresponding to digital diagnosticdata for the repeater onto the data signal.
 23. The repeater of claim21, wherein the out-of-band logic is a microprocessor.